1. Field of the Invention
The present invention relates to the method of programming field devices, and more particularly to the reprogramming of field devices associated with a multidrop network of intelligent devices as utilized in the field of industrial control.
2. Background Art
In the past, it has been exceedingly difficult to reprogram memories associated with field devices as utilized in areas of industrial control. Among several solutions that have been utilized in the past, include the provision of a separate interface to the field device to be controlled, such as a serial port or similar access arrangement for downloading information. Such reprogramming typically takes place by removing the control device from the line. This solution frequently is inadequate inasmuch as it may require the operator to go to the field device in order to connect a downloading device, such as a personal computer. Obviously, this is very inconvenient and time consuming and subsequently the most expensive way of achieving the necessary reprogramming of a field device. Because of the location of many field devices, such technique is often impossible to utilize. Because of the nature of the remote devices, their location may be such that they are enclosed in housings outdoors which need to be opened to access the download connection. Such arrangements typically are undesirable because adverse weather conditions can wreak havoc with the delicate electronics utilized in such control devices.
It is also possible in some situations that the amount of current drawn while allowing full communication processing to take place during the time of the download would require substantial additional current handling capability resulting in substantial additional cost. To provide such current effectiveness would be a most expensive solution and place the device at a competitive disadvantage in the marketplace since comparable devices that do not include an online code download feature might be drawing less current. Accordingly, this download feature is not a requirement in the present invention.
Accordingly, it is the object of the present invention to permit the design of hardware flexible enough to permit current swapping, that is, to utilize the available current for normal operations, or instead, the same amount of current becomes available over the bus network to be utilized for reprogramming, instead of for process operation. Additionally, the use of the communication and power bus as a technique for the technology is different than has been utilized previously in the field of industrial control devices. Other features include software to control the processor speed depending on the functions being performed, thus resulting in the lower current requirements. Finally, it is yet another feature of the present invention to program memory of a low power field device while communicating online.